In the face of concern over water scarcity, nitrate pollution, soil erosion and the effects of pesticides, some people believe organic farming is the only way forward.

The processes used by organic farmers naturally generate soil nutrients and keep the soil fertile, they say.

This, they argue, makes organic farming viable, while other farming methods will only delay mass starvation because they will eventually destroy the environment.

They also fear that covering crops with chemicals, using drugs in meat production and genetically modifying plants could damage both human and animal health.

Others believe intensive farming offers the solution.

They reject organic farming because they feel it is too inefficient to produce food for so many people - an argument often countered by environmentalists who insist that in the long run organic farming is more, not less, efficient.

Intensive farming proponents insist that modern machines and genetic modification make the most of the land available, while modern fertilizers and pesticides keep crops free of disease.

Some scientists even go as far as suggesting that the world's grain output is double what it would be if all synthetic fertilizers were removed overnight.

Others insist that biotechnology companies offer hope in our desperate struggle to feed the world - if, that is, they are willing to share their secrets with the poor.

Five years since the first genetically modified crops went on sale, the environmental benefits and increases in efficiency have not been as dramatic as was hoped - although GM companies point to postive signs, such as reduced pesticide use among farmers growing their crops.

And many of the scary effects which opponents had warned about - such as an explosive rise in 'superweeds' resistant to attempts to destroy them - have also failed to materialise.

But campaigners remain concerned about possible warnings, such as studies which have shown evidence of genes jumping from genetically modified crops to weeds growing alongside them.

However, since the sceptics' main warning has focused on potential long-term effects, it is far too early to say whether or not they were right all along.